1. Field
The following description relates to a method and an apparatus for testing thermal insulation performance of a heat shield coating layer, and to a method and an apparatus for evaluating heat-shielding performance of a coating layer formed on a gas turbine component using cooling air and a high temperature electric furnace.
2. Description of Related Art
One of core components of a gas turbine is the blades. The blades operate under a high-temperature and high-pressure condition. For example, depending on the gas turbine, the blades may be exposed to an environment having a temperature that reaches 200° C., 600° C., or even 900° C. Thus, the blades are subjected to an environment that may easily cause corrosion and oxidation. Further, the blades are subject to a strong centrifugal force due to the high-speed rotation of the blades. Accordingly, the blades are subjected to a high degree of mechanical fatigue. In order to protect the mechanical integrity of the blades and to protect the blades from its high temperature and high pressure environments while maintaining durability, a heat shield coating layer made of a ceramic material is formed around the blade to reinforce its heat shield performance. However, the heat shield coating layer applied to a surface of the blade may also be subject to thermal and mechanical fatigue. Therefore, in order to obtain reliability of a blade of a gas turbine, it is necessary to evaluate the performance of the blade that includes a heat shield coating layer.
Techniques used to evaluate the performance of a heat shield coating layer of a gas turbine component includes a method of testing a blade to which a thermal shield coating has been actually applied. But it is difficult to measure and evaluate the performance of the blade due to high material cost and complicated shape of the blade. Therefore, a method of evaluating the performance of a heat shield coating layer of a blade is generally performed on a test piece extracted from the blade.
Such a method of evaluating the heat shield performance is generally conducted by simply measuring the heat conductivity, which requires a test piece of a far more exaggerated thickness than the thickness of a ceramic coating layer that is actually applied. Thus, there exists much difficulty in manufacturing a test piece.
However, as it is not accurate to regard a test piece having an exaggerated thickness as an accurate duplication of a heat shield coating layer under an actual conduction, the reliability of measurement may be reduced by using the test piece.
Furthermore, an existing test method cannot evaluate the effects of a bond coating layer that is applied to the blade to combine the metal surface of the test piece with a ceramic coating layer or evaluate the effects resulting from the complicated shapes of various layers and the interfaces between the layers.